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README.cygwin - Perl for Cygwin


This document will help you configure, make, test and install Perl on Cygwin. This document also describes features of Cygwin that will affect how Perl behaves at runtime.

NOTE: There are pre-built Perl packages available for Cygwin and a version of Perl is provided on the Cygwin CD. If you do not need to customize the configuration, consider using one of these packages:


Cygwin = GNU+Cygnus+Windows (Don't leave UNIX without it)

The Cygwin tools are ports of the popular GNU development tools for Win32 platforms. They run thanks to the Cygwin library which provides the UNIX system calls and environment these programs expect. More information about this project can be found at:

A recent net or commercial release of Cygwin is required.

At the time this document was last updated, Cygwin 1.1.5 was current.

NOTE: At this point, minimal effort has been made to provide compatibility with old (beta) Cygwin releases. The focus has been to provide a high quality release and not worry about working around old bugs. If you wish to use Perl with Cygwin B20.1 or earlier, consider using perl5.005_03, which is available in source and binary form at If there is significant demand, a patch kit can be developed to port back to earlier Cygwin versions.

Cygwin Configuration

While building Perl some changes may be necessary to your Cygwin setup so that Perl builds cleanly. These changes are not required for normal Perl usage.

NOTE: The binaries that are built will run on all Win32 versions. They do not depend on your host system (Win9x/WinME, WinNT/Win2K) or your Cygwin configuration (ntea, ntsec, binary/text mounts). The only dependencies come from hard-coded pathnames like /usr/local. However, your host system and Cygwin configuration will affect Perl's runtime behavior (see "TEST").


The default options gathered by Configure with the assistance of hints/ will build a Perl that supports dynamic loading (which requires a shared libperl.dll).

This will run Configure and keep a record:

./Configure 2>&1 | tee log.configure

If you are willing to accept all the defaults run Configure with -de. However, several useful customizations are available.

Strip Binaries

It is possible to strip the EXEs and DLLs created by the build process. The resulting binaries will be significantly smaller. If you want the binaries to be stripped, you can either add a -s option when Configure prompts you,

Any additional ld flags (NOT including libraries)? [none] -s
Any special flags to pass to gcc to use dynamic linking? [none] -s
Any special flags to pass to ld2 to create a dynamically loaded library?
[none] -s

or you can edit hints/ and uncomment the relevant variables near the end of the file.

Optional Libraries

Several Perl functions and modules depend on the existence of some optional libraries. Configure will find them if they are installed in one of the directories listed as being used for library searches. Pre-built packages for most of these are available at

Configure-time Options

The INSTALL document describes several Configure-time options. Some of these will work with Cygwin, others are not yet possible. Also, some of these are experimental. You can either select an option when Configure prompts you or you can define (undefine) symbols on the command line.

Suspicious Warnings

You may see some messages during Configure that seem suspicious.


Simply run make and wait:

make 2>&1 | tee log.make


Warnings like these are normal:

warning: overriding commands for target <file>
warning: ignoring old commands for target <file>

dllwrap: no export definition file provided
dllwrap: creating one, but that may not be what you want


During `make', ld2 will be created and installed in your $installbin directory (where you said to put public executables). It does not wait until the `make install' process to install the ld2 script, this is because the remainder of the `make' refers to ld2 without fully specifying its path and does this from multiple subdirectories. The assumption is that $installbin is in your current PATH. If this is not the case `make' will fail at some point. If this happens, just manually copy ld2 from the source directory to somewhere in your PATH.


There are two steps to running the test suite:

make test 2>&1 | tee log.make-test

cd t;./perl harness 2>&1 | tee ../log.harness

The same tests are run both times, but more information is provided when running as `./perl harness'.

Test results vary depending on your host system and your Cygwin configuration. If a test can pass in some Cygwin setup, it is always attempted and explainable test failures are documented. It is possible for Perl to pass all the tests, but it is more likely that some tests will fail for one of the reasons listed below.

File Permissions

UNIX file permissions are based on sets of mode bits for {read,write,execute} for each {user,group,other}. By default Cygwin only tracks the Win32 read-only attribute represented as the UNIX file user write bit (files are always readable, files are executable if they have a .{com,bat,exe} extension or begin with #!, directories are always readable and executable). On WinNT with the ntea CYGWIN setting, the additional mode bits are stored as extended file attributes. On WinNT with the ntsec CYGWIN setting, permissions use the standard WinNT security descriptors and access control lists. Without one of these options, these tests will fail:

Failed Test           List of failed
io/fs.t               5, 7, 9-10
lib/anydbm.t          2
lib/db-btree.t        20
lib/db-hash.t         16
lib/db-recno.t        18
lib/gdbm.t            2
lib/ndbm.t            2
lib/odbm.t            2
lib/sdbm.t            2
op/stat.t             9, 20 (.tmp not an executable extension)

FAT partitions do not support hard links (whereas NTFS does), in which case Cygwin implements link() by copying the file. On remote (network) drives Cygwin's stat() always sets st_nlink to 1, so the link count for remote directories and files is not available. In either case, these tests will fail:

Failed Test           List of failed
io/fs.t               4
op/stat.t             3

Filetime Granularity

On FAT partitions the filetime granularity is 2 seconds. The following test will fail:

Failed Test           List of failed
io/fs.t               18

Tainting Checks

When Perl is running in taint mode, $ENV{PATH} is considered tainted and not used, so DLLs not in the default system directories will not be found. While the tests are running you will see warnings popup from the system with messages like:

  Error Starting Program
  A required .DLL file, CYGWIN1.DLL, was not found

  perl.exe - Unable to Locate DLL
  The dynamic link library cygwin1.dll could not be found in the
    specified path ...

Just click OK and ignore them. When running `make test', 2 popups occur. During `./perl harness', 4 popups occur. Also, these tests will fail:

Failed Test           List of failed
op/taint.t            1, 3, 31, 37

Alternatively, you can copy cygwin1.dll into the directory where the tests run:

cp /bin/cygwin1.dll t

or one of the Windows system directories (although, this is not recommended).


Cygwin does not require /etc/group, in which case the op/grent.t test will be skipped. The check performed by op/grent.t expects to see entries that use the members field, otherwise this test will fail:

Failed Test           List of failed
op/grent.t            1

Script Portability

Cygwin does an outstanding job of providing UNIX-like semantics on top of Win32 systems. However, in addition to the items noted above, there are some differences that you should know about. This is a very brief guide to portability, more information can be found in the Cygwin documentation.


This will install Perl, including man pages.

make install | tee log.make-install

NOTE: If STDERR is redirected `make install' will not prompt you to install perl into /usr/bin.

You may need to be Administrator to run `make install'. If you are not, you must have write access to the directories in question.

Information on installing the Perl documentation in HTML format can be found in the INSTALL document.


These are the files in the Perl release that contain references to Cygwin. These very brief notes attempt to explain the reason for all conditional code. Hopefully, keeping this up to date will allow the Cygwin port to be kept as clean as possible.

Changes Changes5.005 Changes5.004 Changes5.6
pod/perl.pod pod/perlport.pod pod/perlfaq3.pod
pod/perldelta.pod pod/perl5004delta.pod pod/perl56delta.pod
pod/perlhist.pod pod/perlmodlib.pod pod/buildtoc.PL pod/perltoc.pod
Build, Configure, Make, Install
Configure             - help finding hints from uname,
                        shared libperl required for dynamic loading
Makefile.SH           - linklibperl
Porting/patchls       - cygwin in port list
installman            - man pages with :: translated to .
installperl           - install dll/ld2/perlld, install to pods
makedepend.SH         - uwinfix
t/io/tell.t           - binmode
t/lib/b.t             - ignore Cwd from os_extras
t/lib/glob-basic.t    - Win32 directory list access differs from read mode
t/op/magic.t          - $^X/symlink WORKAROUND, s/.exe//
t/op/stat.t           - no /dev, skip Win32 ftCreationTime quirk
                        (cache manager sometimes preserves ctime of file
                        previously created and deleted), no -u (setuid)
Compiled Perl Source
EXTERN.h              - __declspec(dllimport)
XSUB.h                - __declspec(dllexport)
cygwin/cygwin.c       - os_extras (getcwd, spawn)
perl.c                - os_extras
perl.h                - binmode
doio.c                - win9x can not rename a file when it is open
pp_sys.c              - do not define h_errno, pp_system with spawn
util.c                - use setenv
Compiled Module Source
ext/POSIX/POSIX.xs    - tzname defined externally
                      - EXTCONST needs to be redefined from EXTERN.h
                      - binary open
Perl Modules/Scripts
lib/            - hook to internal Cwd::cwd
                      - require
                      - canonpath, cflags, manifypods, perl_archive
lib/File/      - on remote drives stat() always sets st_nlink to 1
lib/File/Spec/ - preserve //unc
lib/File/      - no directory sticky bit
lib/        - use stdin not /dev/tty
utils/perldoc.PL      - version comment


When make starts, it warns about overriding commands for perlmain.o.

`make clean' does not remove library .def or .exe.stackdump files.

The ld2 script contains references to the source directory. You should change these to $installbin after `make install'.

Support for swapping real and effective user and group IDs is incomplete. On WinNT Cygwin provides setuid(), seteuid(), setgid() and setegid(). However, additional Cygwin calls for manipulating WinNT access tokens and security contexts are required.

When building DLLs, `dllwrap --export-all-symbols' is used to export global symbols. It might be better to generate an explicit .def file (see Also, DLLs can now be build with `gcc -shared'.


Charles Wilson <>, Eric Fifer <>, alexander smishlajev <>, Steven Morlock <>, Sebastien Barre <>, Teun Burgers <>.


Last updated: 9 November 2000